1. Field of the Invention
This invention relates to a two-part curable grouting composition and method for grouting structures and formations, such as sewer lines, to minimize or prevent water leakage through voids, joints, cracks, fissures or other openings therein. In another aspect it relates to the structures and formations so sealed.
2. Description of the Background Art
There are a host of water-bearing or holding structures, such as sewer lines, aqueducts, tunnels, wells, settling ponds, and basements of buildings, made of materials such as siliceous materials (e.g., concrete, brick and mortar), plastics (e.g., polyvinylchloride), cast iron, or wood (e.g., cypress or cedar). Because of the nature of such construction materials or the manner of constructing such structures or their locations, such structures inherently have, or develop with time, various discontinuities such as openings, cracks, fissures, joints, or the like which provide an entry or pathway for the undesirable ingress or egress of water into or from such structures. Even hairline cracks or pin-hole size openings in an otherwise sound or water-impervious structure can result in damaging and costly leakage from a temporary or permanent water source.
Water-holding structures, such as concrete irrigation water courses, aqueducts, earthen dams, or dikes, bearing a static head or flowing stream of water, also experience leakage due to holes, cracks, fissures, and the like, such leakage being an uneconomical loss of water as well as hazardous in many circumstances.
A host of grouting compositions and sealing techniques have been used to prevent the ingress or egress of water into or from such structures.
Curable polyurethane compositions containing isocyanate-terminated prepolymers based on polyols have been disclosed as grouting compositions and sealing agents for sewers and similar uses (see U.S. Pat. No. 3,985,688, Canadian Pat. No. 1,035,521 and British Patent Specification No. 1,486,232). Latex reinforced curable polyurethane compositions comprising isocyanate-terminated prepolymers based on polyols have also been disclosed for such uses (see U.S. Pat. No. 4,315,703). Also known is the use of curable isocyanate prepolymers with water to consolidate soil (see U.S. Pat. No. 3,719,050). These prior isocyanate-terminated prepolymer compositions frequently have limited utility, however, because of one or more reasons. Some may cure to form a tough, highly cohesive mass making it difficult to remove contacting equipment after curing. Others may undergo dramatic volume fluctuations with changing environmental conditions, such as changes in moisture conditions. Such volume changes make it difficult to maintain an adequate seal of, for example, a leaking sewer line.
Curable monomer compositions comprising aqueous solutions of magnesium diacrylate and alkali metal monoacrylate or hydroxyalkyl monoacrylate have been disclosed for grouting joints and/or cracks in sewer conduits (see U.S. Pat. Nos. 4,312,605 and 4,318,835). These compositions require use of high levels of monomer to achieve good strength in the cured grout. Also an aqueous solution of a water soluble diacrylate ester of a polyoxyalkylene glycol monomer has been disclosed as a grout for stabilizing soil during tunneling or underground construction (see U.S. Pat. No. 4,295,762). However, this composition may lack sufficient stability when exposed to water for long periods of time, particularly where the water contains acidic or basic materials.
Perhaps the most successful commercially acceptable composition for sewer grouting is based upon acrylamide, typically in an aqueous solution, which is pumped with specially designed equipment into the site of the leak and into the surrounding soil to form a cured gel which inhibits or prevents leaking. In fact, much of the sewer sealing equipment employed in the United States and in other countries has been designed to utilize such acrylamide-type sealing compositions. Such compositions are desired, not only for their ability to appropriately seal leaks in sewers and in other areas, but also because of their viscosity range is easily adjustable, thus providing an easily pumpable mixture, their desirable cure rate and their physical properties achieved upon curing.
The cured acrylamide material generally has an acceptable compressive strength capable of withstanding the compressive forces encountered in sealing situations such as in sewers and when used to bind soil masses and an acceptable resistance to shrinking which is required for the cured material to function properly as a sealant as hydrological conditions vary at the sealing site. Additionally, the acrylamide type sealing compositions will cure in a reasonably brief period of time so that equipment may be advanced to new sealing locations. This is important when sealing sewer lines, for example, where a sewer packer is employed utilizing an inflatable sleeve which is required to be inflated within the sewer line being sealed until the curing of the sealant has been accomplished.
Acrylamide-type sealing compositions also cure to a somewhat weakly cohesive mass which permits easy removal of the application equipment, e.g., the sewer packer, so that the equipment may be moved to a new location without difficulty.
While the acrylamide-type sealing compositions have all these desirable properties and have proven to be extremely valuable in such applications, they have several serious defects including a serious toxicological problem which has limited their use. Acrylamide-type sealing compositions pose toxicological problems both to workers involved in the application of such compositions who may directly contact the acrylamide and to those later exposed to the liquids which pass through structures sealed with such compositions where unreacted acrylamide is present. That acrylamide is a neurotoxic material, and repeated exposure without normal handling precautions may lead to reversible disturbances of the central nervous system and that in at least one instance, acrylamide contamination of a well, resulting in mild acrylamide poisoning of well users, caused a ban on the use of the product in Japan is taught in Kirk-Othmer, Encylopedia of Chemical Technology, John Wiley & Sons, Third Ed., Vol. 5, p. 371 (1979). This situation requires the replacement of the acrylamide-type sealants with a suitable substitute.
The acrylamide-type sealants also create quantities of steam on reacting at the location of the leak. The creation of steam at the location of the leak. The creation of steam at the location of the leak is very undesirable since the steam interferes with the use of remote viewing equipment such as a television camera.